A tube about 11 cm long held open by 16 to 20 C-shaped rings of cartilage, with the gap facing backwards
Trachea — the windpipe.
Anatomy · Organs & viscera
Trachea
The windpipe
Neck and thorax · respiratory system
The trachea, or windpipe, is the flexible tube about 10 to 12 cm long that carries air from the larynx to the lungs. It starts at the lower border of the cricoid cartilage at about C6, runs down in the midline of the neck and into the chest, and divides at the carina into the right and left main bronchi at about T4 to T5. Its front and sides are held open by C-shaped rings of hyaline cartilage.
How to spot them
- ▸A midline tube in front of the oesophagus, with 16 to 20 C-shaped cartilage rings whose open side faces backwards
- ▸The gap in the rings is closed by the trachealis muscle, so the back wall is flat and soft
- ▸Begins below the cricoid cartilage and ends at the carina, where it forks into two main bronchi
- ▸Covered in the neck by the thyroid isthmus, which lies across the second to fourth rings
What to know
The sharp keel-like ridge at its lower end, where it splits into two, very sensitive to touch and provoking a cough
The carina of the trachea, at the level of the sternal angle (T4/T5).
The band of smooth muscle that closes the back of the cartilage rings and lies against the oesophagus
The trachealis muscle of the trachea.
The tube opened in an emergency operation through the second to fourth rings, below the thyroid isthmus
Tracheostomy — an opening into the windpipe.
Lined by ciliated cells and goblet cells which sweep trapped dust and mucus up towards the throat
The mucociliary escalator of the trachea.
Lies in front of the oesophagus, with the arch of the aorta crossing on its left and the brachiocephalic trunk in front
Trachea — its relations in the superior mediastinum.
Its lower end lies at the level of T4 to T5 in quiet breathing, but the level falls to about T6 in deep inspiration
The tracheal bifurcation (carina) moves down when the chest expands.
Key ideas
- The rings stop the airway collapsing when the pressure inside falls during a deep breath, while the soft back lets the oesophagus expand when a large bolus of food is swallowed.
- The mucociliary escalator traps particles on a sheet of mucus and cilia beat it upwards to be swallowed or coughed out.
Quick-fire facts
- •It is about 10 to 12 cm long and about 2 cm across in adults, with 16 to 20 incomplete cartilage rings.
- •It begins at the lower border of the cricoid cartilage (C6) and divides at the carina at the level of the sternal angle (T4/T5).
- •The cartilage rings are hyaline; the first is broader and may fuse with the cricoid, and the last is hook-shaped and forms part of the carina.
- •The lining is pseudostratified ciliated columnar epithelium with goblet cells.
- •The isthmus of the thyroid lies across the second to fourth rings, which is why a tracheostomy is done below or through it.
- •The right main bronchus is wider, shorter and more vertical than the left, so inhaled objects tend to lodge on the right.
- •The left recurrent laryngeal nerve runs in the groove between the trachea and oesophagus.
- •The trachea is not visible on the surface but can be felt in the midline in the suprasternal notch; a deviated trachea points to disease in the chest.
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